Fuel lines composed of synthetic resin have been produced heretofore by extrusion-pressing for conducting normal gasoline or high-test or supergasoline from the gasoline tank or reservoir of the vehicle to an internal combustion engine.
Such lines, which generally have lengths of at least several meters, must be provided with narrow tolerances for both the installation of the line in the vehicle and for the proper functioning thereof. Furthermore, it is important, once the line has been installed, that it not change materially in length during operation, either by shrinkage or elongation or as a result of the stresses to which the line may be subject in use. Shrinkage once the ends of the line are fixed, for example, can result in breakage. Elongation can cause bowing of the line where such bowing may be hazardous to continued operation because it may bring the line into proximity of a dangerous condition or result in kinking.
Not unsurprisingly, conventional fuel lines fullfil these requirements when they are used for ordinary gasoline or super-gasolines.
When, however, the fuel contains alcohol, i.e. is a gasohol, and especially when the alcohol is methanol, even the conventional gas lines which normally do not undergo length changes, are found to be subject to detrimental length changes such that the length may increase some 4 to 5% and some 10 to 20 cm in extreme cases.
Since conventional extruded synthetic resin tubes using polyamide walls in contact with the fuel cannot be employed because of these length changes, it has been customary for vehicles which were predominantly to be fueled by normal gasoline or supergasoline admixed with alcohol, to substitute metal fuel lines.
However, metal fuel lines are subject to corrosion by alcohol-containing fuel, internally as well as subject to external corrosion, the internal corrosion apparently being a result of the strong hygroscopic character of the alcohols so that it is practically impossible to ensure that the alcohol in the fuel will not carry along at least some water.
However, with the increasing need for replacement of lead-containing gasolines, and especially supergasolines with lead-free supergasoline, the need to admix alcohol with the gasoline for good antiknock properties are increased. These factors also apply to Diesel fuels in cases in which alcohol must be added thereto for various reasons.
Up to now, therefore, compromises were required with respect to the fuel lines used and the fuel employed.